© 2015 Dr. Joachim Nerz (1 of 53)
Little information has been published on larval morphology. Captive bred larvae have been recorded to have an average total length 11.5 - 14.5 mm at hatching, growing to lengths of 40 - 70 mm at metamorphosis (Bogaerts et al. 2012). Larvae tend to be slender-bodied, with low dorsal fins extending from the middle of the back to the rounded end of the tail (Steinfartz et al. 2002). Short external gills are present (Schmidt 1939).
Neurergus strauchii, N. crocatus, and N. derjugini (formerly N. microspilotus) are similar looking species, all with bright yellow spots occurring on a grey-black ground color. However, N. strauchii have smaller and more numerous yellow dorsal spots than N. crocatus. Spots of N. strauchii are also more uniformly sized than the irregular yellow blotches found on of N. derjugini. Additionally, the venters of N. crocatus and N. derjugini are completely yellow, orange or carmine red rather than displaying a narrow orange band on black that is affiliated with N. strauchii (Sparreboom 2014).
In life, the background color is dark brown to grey-black. Numerous yellow rounded spots with average diameters of 2.4 mm in N. s. barani, 1.3 mm in N. s. munzurensis, and 2.2 mm in N. s. strauchii are scattered across the dorsal surface of body, including the head, trunk, limbs and tail (Olgun et al. 2016). The blackish ground color continues ventrally, where it eventually interrupted by a narrow, wavy orange line that extends from the gular region to tip of the tail (Baran and Öz 1986). This orange midline can be continuous or interrupted by patches of the dark background color (Pasmans et al. 2006). Smaller yellow-orange dots might also extend onto the throat or along underside of the limbs (Baran and Öz 1986). Some sexual dimorphism has been noted in the coloration of this species. In males, silver-blue spots develop along the lateral sides of the tail and body during breeding season, sometimes forming a stripe (Sparreboom et al. 2000; Sparreboom 2014). This trait is unique to the N. strauchii, and is the only known color-based sexual dimorphism within the genus (Sparreboom et al. 2000).
In life, young larvae start off light grey with many fine black dots (Schmidtler and Schmidtler 1975). As they age, two rows of light spots and two irregular rows of dark spots develop along their back while their tails become increasingly dark-pigmented (Schmidtler and Schmidtler 1975). After a few weeks, the lateral line system becomes visible in the form of stripes along the body and tail, and golden dots behind the eyes (Bogaerts et al. 2012). After three to four months, yellow spots form and the ground coloration darkens (Bogaerts et al. 2012).
The three subspecies can be differentiated by the size and density or number of spots, and by body metrics. More specifically, spots on N. s. barani and N. s. strauchii are larger than N. s. munzurensis, with the range of diameters being 1.6 – 3.3 mm, 1.7 – 2.8 mm, and 1.1 – 1.8 mm respectively. The density of spots in N. s. barani, N. s. munzurensis, and N. s. strauchii are respectively 3.4, 8.7, 6.8 spots/cm2 (Olgun et al 2016). The number of spots follows a trend of increasing in as populations are found further east (Sparreboom 2014). The species can also be differentiated by geography. Neurergus s. barani are the mountain dwelling subspecies near Malatya in the west, and have fewer spots than N. s. strauchii in the east (Sparreboom 2014, Pasmans et al. 2006). Neurergus s. munzurensis displays the greater number of spots, but the diameter of each is significantly smaller than any subspecies (Olgun et al. 2016). Furthermore, both N. s. barani and N. s. strauchii are significantly larger than N. s. munzurensis in total length, body length (both measuring from the snout to posterior and anterior of the cloaca), tail length, and fore- and hindlimb lengths (Olgun et al 2016).
There is also evidence of some sexual dimorphism in N. strauchii. Males are typically more slender-bodied with relatively shorter tails than their female counterparts (Bogaerts et al. 2012). Male cloacas are also larger and rounded in shape with a longitudinal slit while female cloacas are more conical with a round opening (Sparreboom 2014). Female cloacas are also evenly colored orange while male cloacal coloration is patchy (Bogaerts et al. 2012).
Distribution and Habitat
Outside of the breeding season, adults may be found on land hiding under rocks or hibernating in burrows (Papenfuss et al. 2009, Schmidtler and Schmidtler 1970). During the terrestrial phase, Bogaerts et al. (2006) were only able to find adults in rocky habitats where trees and shrubs were scarce or absent.
Life History, Abundance, Activity, and Special Behaviors
The average age of wild-caught N. strauchii ranges from 6 - 16 years. The average age in males is 8.8 years and the average in females is 10.9 years. The oldest caught N. strauchii male was 14 years old and the oldest caught female was 16 years old (Yakin et al. 2015). In captive salamanders, sexual maturity was attained after 3 - 4 years and in wild species, this usually occurs after 4 - 5 years (Sparreboom 2014, Yakin et al. 2015)
Neurergus strauchii adults emerge from hibernation in early spring and migrate during or after the snow melts into the streams where they will mate and breed. After spawning, adults will leave the water and return to land; this migration to land usually happens at night (Schneider and Schneider 2010). Adults will overwinter on land under rocks or in burrows within scattered oaks near streams (Schmidtler and Schmidtler 1970). There is not enough information on the duration of this adult aquatic phase to accurately say how long it usually is.
The breeding season usually begins at the end of April to the beginning of May and ends in June (Pasmans et al. 2006). It may continue a little longer after June depending on geographic region (Tok et al. 2016). During the breeding season, adults are usually found in high mountain streams 1,000 - 1,900 m above sea level (Bogaerts et al. 2012). Streams where N. strauchii breed tend to have a pH between 7 and 9 (Pasmans et al. 2006). Water temperatures in these streams have been recorded as low as 5.8 °C at the beginning of the breeding season (Bogaerts et al. 2012) to as high as 21.9 °C at the end of the breeding season (Schneider and Schneider 2010).
Neurergus strauchii breed in fast-moving mountain streams and brooks, preferably with large and deep slow-running pools (Steinfartz et al. 2002, Bogaerts et al. 2012). Breeding typically occurs in water where temperatures range from 9 - 17°C and it is suggested by Bogaerts et al. (2012) that water temperatures at the high end of this range may speed up the development of larvae or change the timing of the adult phase. Streams where most breeding occurs tend to have dense riparian vegetation and low amounts of erosion on streamside due to humans or grazing (Schneider and Schneider 2010).
In courtship behavior experiments, Sparreboom et al. (2000) observed males position themselves on a heap of stones in the water and actively survey their surroundings. Once a male spots a female, he pursues her, attempting to get in front of her. The male turns so he is face-to-face with the female, standing only centimeters apart. He bends his tail against his side that is closest to the female and fans it outward towards her snout. He may move or change sides in an attempt to stay directly in front of the female. He may pause for 5 - 7 seconds and then continue fanning. He will alternate fanning and pausing. The male then turns away from the female and slowly walks away, making rapid, undulating movements with his tail. If the female is responsive, she will follow the male, sometimes slowly undulating or fanning her own tail. She will touch his tail with her snout several times. After a number of tail-touches, the male deposits a spermatophore. The male will walk forward and pivot approximately 90° so he is perpendicular with the female, known as a “brake”. This behavior blocks her from moving ahead and causes her to stop where her cloaca is directly over the spermatophore. She stops and it sticks to her cloaca. Males may continue walking and depositing more spermatophores or begin fanning again (Sparreboom et al. 2000).
Sexual interference has been observed in both sexes. Other males may move between a courting pair and take over the courtship process. Another female may also interrupt a pair while courting and follow the male herself (Sparreboom et al. 2000).
Ovipositioning may occur during the day or at night (Bogaerts et al. 2012).
Eggs are clear and connected by a long jelly string. Each egg capsule measures about 5 - 6mm in diameter. Embryos measure around 2.5 mm in the eggs and when they hatch about a month later, around 12 – 15 mm (Schmidtler and Schmidtler 1970, Bogaerts et al. 2012). Bogaerts et al. (2012) reported eggs in captivity were laid in clutches of 70 - 110 eggs on the undersides of rocks, stones, and boulders; this is also typical for wild populations and many are laid in areas with direct sunlight (Pasmans et al. 2006). There can be as many as 285 eggs in one clutch (Bogaerts et al. 2012). The number of clutches of eggs ranges from 1 - 10 (Schneider and Schneider 2010). Eggs can hatch after as little as 15 days in captivity or as long as 34 days. For the first few days after hatching, larvae live on yolk from the egg and after a few days will begin to eat live food such as microorganisms and small worms (Bogaerts et al. 2012).
Metamorphosis can begin as early as 80 days after hatching but can be observed after 7 - 8 months when the larvae are around 60 - 70mm long (Tok et al. 2016). Neurergus strauchii larvae can postpone metamorphosis and overwinter in their larval form (Tok et al. 2016). The first shedding takes place around the same time as metamorphosis, sometimes just before emerging from the water (Bogaerts et al. 2012). Metamorphosis is very gradual and the juveniles have been observed to switch from water to land and go back and forth for a period of several weeks (Bogaerts et al. 2012).
There is not much information on diet, other than what individuals were fed while in captivity. In a captive breeding experiment, Bogaerts et al. (2012) fed N. strauchii adults many types of insects such as young crickets, mealworms, earthworms, maggots, larvae of wax moths, and slugs when in their terrestrial phase. In water, they were fed many worms species as well as Daphnia species and eggs and larvae from Rana species. They would also eat small guppies and non-living prey like slices of liver and octopus cut in mealworm-like strips fed to them by researchers. They are generally pretty slow at catching prey and didn’t seem to be very voracious when eating.
Trends and Threats
Neurergus strauchii is a “Strictly Protected Species” under the Convention on Conservation of European wildlife and Natural Habitats, which is also called the Bern Convention and was ratified by Turkey in 1984 (Bogaerts et al. 2006). Outside of the Bern Convention mentioned above, Turkey does not currently provide legal protection for amphibian species (Pasmans et al. 2006).
During surveys for the species, Bogaerts et al. (2006) witnessed villagers using the streams containing N. strauchii as water sources or for dumping sewage and reported road construction and overgrazing as other possible threats to the species’ terrestrial and aquatic habitats. The authors of the same study also documented adult specimens of N. s. barani that were being sold in Germany, and surmised that adults animals are being collected from the streams during breeding season for the pet trade (Yakin et al. 2015). These newts are sometimes killed by locals who believe that they are venomous or bad luck (Yakin et al. 2015, Olgun et al. 2016).
Diseases are not well documented in wild specimens. Two species of parastitc nematodes, Aplectana acuminata and Cosmocerca commutata, were found in wild N. strauchii specimens but it is not known whether these contribute to the decline (Koyun et al. 2013). Captive bred newts of the genus Neurergus have been diagnosed with metabolic bone disease, ranavirus, chytridiomycosis, chlamydiosis and intestinal parasitosis (Bogaerts et al. 2012).
Relation to Humans
Possible reasons for amphibian decline
General habitat alteration and loss
The genus Neurergus is in the family Salamandridae, and contains three other species: N. crocatus, N. kaiseri and N. derjugini (formerly microspilotus). Neurergus strauchii is split into three subspecies, N. s. strauchii, N. s. barani, and N. s. munzerensis (Olgun et al. 2016).
Based on Bayesian Inference, Maximum Likelihood, and Maximum Parsimony analysis of morphological characters and 833 base pairs of combined 12S and 16S rRNA sequences, N. strauchii is sister to the clade formed by N. crocatus, N. kaiseri, and N. derjugini (Özdemir et al. 2009).
Özdemir et al. (2009) did not find significant morphological or genetic differences between the subspecies, N. s. strauchii and N. s. barani, suggesting that the two subspecies are still connected or only recently became separated.
Ommatotriton is the most closely related genus to Neurergus (Özdemir et al. 2009).
This species was first described in 1887 by Dr. Franz Steindachner of the Imperial Academy of Sciences in Vienna. Steindachner placed the species in the genus Molge. Nearly forty years later, in 1926, Walterstorff reclassified the species as Triton crocatus forma strauchii and then, in 1939, Schmidt described it as a subspecies of Neurergus crocatus. In 1970, Schmidtler and Schmidtler returned its status as a full species placing it in the genus Neurergus, which was confirmed by Baran and Öz (1986). In 1994, Öz separated the species into two subspecies, N. s. strauchii and N. s. barani (as cited in Olgun et al. 2016) and a third subspecies, N. s. munzurensis, was suggested by Olgun et al. in 2016.
The etymology for the subspecies N. s. munzerensis is derived from the location the subspecies was found, the Munzur Valley National Park (Olgun et al. 2016).
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Written by Ashley Rath, Ruby Rebensdorf, Madeleine Wieland (rrrebensdorf AT ucdavis.edu, mjwieland AT ucdavis.edu, arrath AT ucdavis.edu), University of California Davis
First submitted 2018-03-13
Edited by Ann T. Chang (2018-03-14)
Species Account Citation: AmphibiaWeb 2018 Neurergus strauchii <http://amphibiaweb.org/species/4261> University of California, Berkeley, CA, USA. Accessed Dec 6, 2019.
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Citation: AmphibiaWeb. 2019. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 6 Dec 2019.
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